openenv/pr_813/en/environments/connect4.md

Connect4 Environment

A classic Connect Four board game environment for training agents on turn-based strategy with a 6×7 grid. Players alternate dropping pieces into columns, aiming to connect four in a row horizontally, vertically, or diagonally.

Quick Start

import asyncio
from connect4_env import Connect4Action, Connect4Env

async def main():
    async with Connect4Env(base_url="http://localhost:8000") as client:
        obs = await client.reset()
        print(f"Board: {obs.board}")
        print(f"Legal moves: {obs.legal_actions}")

        # Drop a piece in column 3
        result = await client.step(Connect4Action(column=3))
        print(f"Reward: {result.reward}, Done: {result.done}")

asyncio.run(main())

Action Space

Field	Type	Description
column	int	Column index (0–6) where the piece will be dropped

Invalid moves (out-of-range or full column) result in a reward of -1 and end the episode.

Observation Space

Field	Type	Description
board	list[list[int]]	6×7 grid — 1 = current player, -1 = opponent, 0 = empty
legal_actions	list[int]	Column indices that are valid moves

Rewards

Outcome	Reward
Win (4 in a row)	+1.0
Draw (board full)	0.0
Invalid move	-1.0
Otherwise	0.0

State

Field	Type	Description
episode_id	str	Unique ID for the current game
board	list[list[int]]	Current board state
next_player	int	Whose turn it is (1 or -1)
step_count	int	Number of steps taken